Influenza activity is increasing in many European countries, although the epidemic may have passed its peak in some countries, mostly in north-western Europe, concludes the Weekly Influenza Surveillance Overview, Week 4, 2013.
For week 4, two-thirds of the 29 countries reporting have indicated medium-intensity transmission, wide geographic spread and increasing trends in a range of combinations.
Virological surveillance in week 4 shows that the proportion of influenza-positive cases among sentinel specimens was high (52%), representing an increase from 45% on week 3/2013.
Since week 40/2012, an even distribution of influenza virus types has been observed, 50% each for type A and type B viruses. Among influenza A viruses, an increasing proportion of A(H1)pdm09 over A(H3) has been reported during the past two weeks. The virological pattern in Europe continues to be different from that being reported in North America where A(H3) viruses are dominant.
ECDC continues to monitor and report influenza activity in Europe on weekly basis throughout the season.